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Most runners run too hard. We log the majority of our miles at moderate- and high-intensity speeds, barely deigning to hit the low-intensity paces that are so essential to building an aerobic base. Yes, running slow takes longer. Yes, you may not feel quite as accomplished postrun. But go too hard too often and instead of seeing performance benefits, you’re more likely to burn out.
Take the case of two groups of recreational runners who were tested in a 2013 study published in the International Journal of Sports Physiology and Performance: One group spent 77 percent of their time doing low-intensity workouts, 3 percent doing moderate-intensity workouts, and 20 percent doing high-intensity workouts, a method called polarized training. The other group spent 46 percent of their time doing low-intensity workouts, 35 percent doing moderate-intensity workouts, and 19 percent doing high-intensity workouts. After 10 weeks, both groups improved their 10K times, but the polarized training group improved by nearly double the amount of time, shaving about 41 seconds off the total time.
And when endurance athletes followed high-volume training, threshold training, high-intensity interval training, or polarized training protocols, it was the last group who showed the most improvements in VO2 max, time to exhaustion, and peak velocity and power, a 2014 study in the journal Frontiers in Physiology found.
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Polarized training is proof that more isn’t always better. Instead, balancing high-intensity efforts that will make you faster with low-intensity efforts that allow for recovery and increased cardio and muscular strength will take you far in the long run.
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So, What Exactly Is Polarized Training?
Polarized training is all about scaling down (or completely ditching) moderate-intensity running to focus on easy and hard efforts.
“Polarized training can be defined on a macro and micro scale,” says Jason Karp, Ph.D., an exercise physiologist, coach, and author of the upcoming book Periodization for Runners: Training Theories to Run Faster. “First, overall training is separated into low-intensity and high-intensity zones, with very little training done in the middle; second, individual easy runs are very easy and hard runs are very hard.”
The polarized training model blocks training intensity into one of three zones, explains Greg Grosicki, Ph.D., an assistant professor and director of the exercise physiology laboratory at Georgia Southern University: low (zone 1), moderate (zone 2), and high (zone 3) intensity. There should be a heavy emphasis on zone 1 training (below the lactate threshold—the intensity of exercise at which lactate begins to accumulate in the blood at a faster rate than it can be removed, and the physiological transition point between aerobic and anaerobic exercise); a lesser amount of zone 3 training (above the lactate threshold); and very little zone 2 training (at or very near lactate threshold; think: tempo runs), says Karp.
But that minimal emphasis on zone 2 (moderate-intensity training) is key. “The biggest problem with these moderate-intensity efforts is that they do not allow us to truly train hard when the time comes,” explains Grosicki—which makes it harder to optimize your training adaptation. “Yet, most recreational athletes spend upwards of 50 percent of their total training time at a moderate intensity,” he adds. “Not only does this leave these individuals too fatigued to push hard during [hard] workouts, but it also greatly increases their susceptibility to injury.”
The benefit of a high-low focus like this is that the “low” work helps you develop your aerobic system to a very high capacity—increasing mitochondrial volume, capillary density, and total volume—while still allowing for high-intensity work that stimulates training adaptations, like improving VO2max by focusing on the heart’s capacity to pump blood and oxygen and improving anaerobic metabolism to improve speed, without burning you out, explains Karp.
How to Maximize Your Easy and Hard Runs
Committing to polarized training means leaving that moderate-intensity zone (a.k.a. the comfort zone for most runners) behind and really dialing in your high- and low-intensity efforts.
You don’t need complex and expensive laboratory equipment to determine your lactate threshold to define these zones, says Grosicki; techniques like heart rate monitoring or even perception of effort can be equally as effective.
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“If monitoring heart rate, aim for a heart rate of well below 80 percent of your maximum heart rate on your easy days; generally something around 70 percent of your max heart rate is a good rule of thumb,” he says. [Here’s a quick guide on estimating your max HR.] If you’re someone who gets too caught up in data and prefers not to wear a heart rate monitor, you can go by your rate of perceived exertion (RPE), too: On easy days, listen to your body and try to keep your effort at a 4 or below on a scale of 1 to 10.
“Low-intensity training may be the most optimal intensity at which to adapt because it comes with the least stressful work,” says Karp. “You could get equal or even greater adaptation with higher-intensity work, but that comes at the price of a lot of fatigue and physiological stress, with [risk of] hormonal disturbances and reduced activity of the sympathetic nervous system.” When too much of your training is high intensity, it can be too demanding and lead to overtraining in as little as two to three weeks.
But if approximately 80 percent of your running is easy, as in the polarized training studies, the other 20 percent of your training has to be hard—like, really hard. “Runners can maximize their high-intensity efforts by running at or very near to their VO2max pace,” says Karp—that corresponds to around 90 percent of your max heart rate, says Grosicki, or a perceived effort of 7 or greater on that 1 to 10 scale. If the interval is long, you’ll work in the lower end (around 90 percent MHR, or 7 to 8 out of 10 effort); if the interval is short, aim for the higher end (95 percent MHR, or 9 to 10 out of 10 effort).
During high-intensity efforts, Grosicki recommends aiming for interval efforts lasting somewhere between 30 seconds and 10 minutes. Four sets of five-minute hard efforts with two-and-a-half minutes of rest in between is a protocol that was used by many of the early training studies in the exercise physiology literature, he says.
Try it:
- Warm up with an easy jog and dynamic drills
- Run 4 x 5 minutes hard (7 or 8 out of 10 effort)
- Jog easy for 2:30 to recover between each interval
- Cool down
Interestingly, a recent study on elite cyclists found that this conventional four by five-minute workout was inferior to incorporating shorter-duration Tabata-style intervals (three rounds of 13 by 30 seconds hard followed by 15 seconds easy or rest).
Try it:
- Warm up with an easy jog and dynamic drills
- Run 13 x 30 seconds hard (9 to 10 out of 10 effort)
- Recover for 15 seconds between each interval
- Repeat the set 3 times total
- Cool down
“With this in mind, a fun and easy workout to follow would be something like five by one minute hard followed by five by 30 seconds hard, with an equal amount or half of the rest time,” Grosicki says.
Try it:
- Warm up with an easy jog and dynamic drills
- Run 5 x 1-minute hard (8 to 9 out of 10 effort)
- Recover for 1 minute between each interval
- Run 5 x 30 seconds hard (9 to 10 out of 10 effort)
- Recover for 30 seconds between each interval
- Cool down
The best way to optimize your hard sessions, though, is by making sure you’re ready, physically and mentally, for the work you’re about to perform, says Grosicki. “Most recreational athletes will train somewhere between four and six times a week. Targeting one to two hard sessions on days when you know you’ll be sufficiently rested and will have the most energy is a good goal.” And by going easy enough on those other days, you should be chomping at the bit and ready to push yourself to the limit.
